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API functions68

4.47

ps4000aSetSigGenArbitrary

PICO_STATUS ps4000aSetSigGenArbitrary (

int16_t handle,

int32_t offsetVoltage, // see note 1

uint32_t pkToPk, // see note 1

uint32_t startDeltaPhase,

uint32_t stopDeltaPhase,

uint32_t deltaPhaseIncrement,

uint32_t dwellCount,

int16_t * arbitraryWaveform, // see note 1

int32_t arbitraryWaveformSize, // see

note 1

PS4000A_SWEEP_TYPE sweepType,

PS4000A_EXTRA_OPERATIONS operation, // see note 1

PS4000A_INDEX_MODE indexMode,

uint32_t shots,

uint32_t sweeps,

PS4000A_SIGGEN_TRIG_TYPE triggerType,

PS4000A_SIGGEN_TRIG_SOURCE triggerSource,

int16_t extInThreshold

)

This function programs the signal generator to produce an arbitrary waveform.

The arbitrary waveform generator uses direct digital synthesis (DDS). It maintains a

32-bit phase accumulator that indicates the present location in the waveform. The top

bits of the phase accumulator are used as an index into a buffer containing the

arbitrary waveform. The remaining bits act as the fractional part of the index, enabling

high-resolution control of output frequency and allowing the generation of lower

frequencies.

The generator steps through the waveform by adding a deltaPhase value between 1

and phaseAccumulatorSize-1 to the phase accumulator every dacPeriod (1/

dacFrequency). If deltaPhase is constant, the generator produces a waveform at a

constant frequency that can be calculated as follows:

( ) ( )

outputFrequency =

dacFrequency ×

deltaPhase

phaseAccumulatorSize

awgBufferSize

arbitraryWaveformSize

where:

outputFrequency = repetition rate of the complete arbitrary waveform

dacFrequency = update rate of AWG DAC (see table below)

deltaPhase = calculated from startDeltaPhase and

deltaPhaseIncrement

phaseAccumulatorSize = maximum count of phase accumulator (see table

below)

awgBufferSize = maximum AWG buffer size (see table below)

arbitraryWaveformSize = length in samples of the user-defined waveform

Parameter

Value

dacFrequency

80 MHz

dacPeriod (= 1/dacFrequency)

12.5 ns

phaseAccumulatorSize

4 294 967 296 (2

)

awgBufferSize

16 384 (2

)